/*
 * Copyright (C) 2007-2012 by XDEV Software, All Rights Reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 3.0 as published by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
 
package xdev.util;

/**
 * 
 * The {@link StringFilter} defines a pattern to filter a given {@link String};
 * 
 * @author XDEV Software (RHHF)
 * 
 * @since 3.0
 */
public interface StringFilter {

	/**
	 * Returns the filtered <code>input</code> {@link String}.
	 * 
	 * @param input
	 *            {@link String} to be filtered.
	 * @return the filtered <code>input</code> {@link String}.
	 */
	public String filter(String input);

	/**
	 * 
	 * A "null pattern" implementation of {@link StringFilter}.
	 * 
	 * @author XDEV Software
	 * 
	 * @since 3.0
	 * 
	 */
	public static class NullStringFilter implements StringFilter {

		/**
		 * "The" {@link NullStringFilter} instance to use for comparison.
		 */
		public static final NullStringFilter NULL_STRING_FILTER = new NullStringFilter();

		/**
		 * Does nothing. Just returns the provided input {@link String}.
		 */
		@Override
		public String filter(String input) {
			return input;
		}

	}
}
